Bright Titanium: The Art and Science of Chemical Polishing

In the vast universe of materials science, titanium has become a shining star in many high-tech fields and daily applications with its unique physical and chemical properties, such as high strength, low density, excellent corrosion resistance and good biocompatibility. Among the many processing technologies of titanium materials, chemical polishing is particularly important as a process that can not only give the material a bright surface effect, but also improve surface performance and corrosion resistance.

Chemical polishing, as the name suggests, is the process of polishing the surface of titanium using the principle of chemical reaction. The core of this process lies in the redox reaction between the polishing liquid and the titanium surface. The polishing liquid usually contains multiple components such as oxidants, chelating agents, buffers and surfactants, which act together on the titanium surface to form a complex chemical reaction system.

During the chemical polishing process, the oxidant in the polishing liquid reacts with the metal atoms on the surface of the titanium material to form titanium oxides or other soluble compounds. These compounds are then stabilized and dissolved by the chelating agent in the polishing liquid, thereby removing tiny particles and oxide layers on the surface. Certain components in the polishing liquid can also undergo further chemical reactions with the surface of the titanium material to form a uniform and dense oxide film. This oxide film can not only improve the brightness and glossiness of the titanium surface, but also enhance its corrosion resistance and protect the titanium material from erosion by the external environment.

The process flow of chemical polishing can be roughly divided into three stages: pretreatment, polishing, and post-treatment.

Pretreatment: Pretreatment is an important step before chemical polishing, which aims to remove oil stains, oxide layers and other impurities on the surface of titanium materials. Common pretreatment methods include alkaline washing, acid washing and electrochemical cleaning. Alkaline washing can remove oil stains and organic matter, acid washing can remove oxide layers and metal ions, and electrochemical cleaning can further remove tiny particles and pollutants on the surface. The quality of pretreatment directly affects the subsequent polishing effect and material properties.

Polishing: Polishing is the core link of the chemical polishing process. In this stage, the pretreated titanium material is immersed in the polishing liquid, and the chemical polishing of the titanium surface is achieved by controlling the parameters such as the ratio, temperature and polishing time of the polishing liquid. The ratio of the polishing liquid needs to be adjusted according to the type of titanium material, the surface state and the required polishing effect. Temperature control affects the rate of chemical reaction and the polishing effect. The length of polishing time determines the degree of polishing and the amount of material loss. During the polishing process, the performance indicators of the polishing liquid, such as pH value, oxidant concentration, etc., need to be regularly tested to ensure the stability and consistency of the polishing process.
Post-treatment: Post-treatment is a necessary step after chemical polishing, which aims to remove the residual chemical components and contaminants in the polishing liquid and further beautify the surface of the titanium material. Common post-treatment methods include water washing, passivation and drying. Water washing can remove the residue in the polishing liquid, and passivation can form a dense protective film on the surface of the titanium material to enhance the corrosion resistance and stability of the material. Drying is to remove the moisture on the surface of the titanium material to avoid water stains and corrosion.

As an efficient surface treatment technology, chemical polishing has many advantages:
Wide range of application: Chemical polishing is suitable for the treatment of titanium materials of various shapes and structures, especially for titanium materials with complex shapes and fine structures, chemical polishing can show its unique advantages.
Good surface quality: Chemical polishing can remove tiny particles and oxide layers on the surface of titanium materials, generate a uniform and dense oxide film, thereby improving the brightness and gloss of the surface, and enhancing the corrosion resistance of the material.
Strong process controllability: By adjusting the ratio, temperature and polishing time of the polishing liquid and other parameters, the polishing effect can be precisely controlled to meet the needs of different application scenarios.

However, chemical polishing also faces some challenges:
Selection and ratio of polishing liquid: The selection and ratio of polishing liquid directly affect the polishing effect and material properties. Different types of titanium materials and different polishing requirements require different polishing liquid formulas. Therefore, in practical applications, it is necessary to optimize and adjust the ratio of polishing liquid according to specific circumstances.
Control of temperature and time: The temperature and polishing time of the polishing liquid have an important influence on the polishing effect. Too high temperature or too long time may lead to excessive polishing, resulting in material loss and increased surface roughness; too low temperature or too short time may lead to insufficient polishing and fail to achieve the expected polishing effect. Therefore, the temperature and time parameters need to be strictly controlled during the polishing process.
Subsequent cleaning and passivation: The surface of the polished titanium material may have residual chemical components and pollutants in the polishing liquid. If the cleaning is not thorough or the passivation treatment is improper, the performance and stability of the material may be affected. Therefore, after polishing, thorough cleaning and passivation treatment are required to ensure the cleanliness and corrosion resistance of the titanium surface.
Environmental protection and safety issues: The polishing liquid used in the chemical polishing process usually contains some harmful substances, such as heavy metal ions, oxidants, etc. The emission and treatment of these substances may cause harm to the environment and human health. Therefore, in the chemical polishing process, it is necessary to strictly abide by environmental protection laws and regulations and safe operating procedures to ensure the rational use of polishing liquid and proper disposal of waste.

As one of the important surface treatment technologies for bright titanium materials, chemical polishing plays an important role in improving material performance and beautifying the surface. However, this process also faces many challenges and limitations. Therefore, in practical applications, it is necessary to comprehensively consider the type, shape structure, polishing requirements, environmental protection and safety factors of titanium materials to formulate a reasonable polishing process plan. It is also necessary to continuously develop new polishing liquid formulas and process technologies to meet the needs and challenges of different application scenarios.